What is the significance of cod

Our real-time COD data fills the gap between grab samples, so you will never miss an unexpected event again. Chemical Oxygen Demand is an important water quality parameter because, similar to BOD, it provides an index to assess the effect discharged wastewater will have on the receiving environment. Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen DO levels.

A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms. Relying on grab samples leads to significant delays. When results come back from the lab, the information is usually of little value for process control and improving plant performance. Two of the most common techniques for COD wastewater removal are:. Wastewater separation techniques remove colloidal solids suspended in wastewater by coagulation and flocculation in wastewater treatment.

In coagulation, a non-toxic agglomerating agent such as Ferric Chloride F e Cl or alum is added to the water to bring all the suspended particles together to form clumps which can easily be removed from wastewater by filtration. Flocculation uses a chemical polymer flocculating agent to precipitate the clumped particles out of the water by forming larger particles, or flocs. The flocs then undergo the sedimentation process in wastewater treatment by being deposited into a sedimentation tank for further treatment prior to disposal.

Another efficient technique for COD removal is to introduce bacteria or microorganisms that break down organic compounds present in the wastewater. Microbes in sewage treatment can be aerobic or anaerobic. Aerobic COD removal introduces microorganisms or bacteria that break down organic compounds present in wastewater into carbon dioxide and water in the presence of air.

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Do not invert the vial again immediately before inserting the vial into the instrument. It is necessary to allow time for undissolved particles to settle to the bottom and out of the light path of the digital instrument.

Chloride is the primary interference when testing for COD. Each COD vial used with the dichromate method contains mercuric sulfate that will eliminate chloride interference up to the level specified in the procedure. TOC measures organic carbon but different organic carbons will generate different oxygen demand. Measuring TOC alone will not necessarily indicate how much oxygen will be consumed by the organics in the environment.

For example, oxalic acid and ethanol produce identical TOC results. However, due to different oxidation states, the oxygen demand of ethanol is 6 times greater than oxalic acid, meaning ethanol will have a greater effect on the dissolved oxygen content of a receiving water.

Measuring oxygen demand rather than TOC produces a clearer picture of how the receiving waters will be affected by the organic-containing wastewaters.

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